Compressed air actuated electric switch



Feb. 10, 1959 H. THOMMEN COMPRESSED AIR ACTUATED ELECTRIC SWITCH Filed Oct. 29, 1957 INVENTOR Hans Tb om men "limb 21% & HAL;

United States Patent V 2,873,331 COMPRESSED AIR ACTUATED ELECTRIC SWITCH Hans Thommen, Baden, Switzerland, assignor to Aktiengesellschaft Brown, Boveri & Cie, Baden, Switzerland, 2 joint stock company Application October 29, 1957, Serial No. 693,185 Claims priority, application Switzerland October 30, 1956 7 Claims. (Cl. 200-148) The present invention relates to compressed gas, e. g. air, actuated electric switches and in particular to those switches designed for the higher ranges of disconnect capacities which, in addition to one or more sets of main contacts used for interrupting the main load current, also include auxiliary contact sets which serve various purposes. The auxiliary contacts may, for example, be arranged to function as an isolating switch for insulating the load from the high voltage power supply point. To carry out this function, the auxiliary contacts are arranged in series with the main contacts and are opened after the main contacts have opened. The auxiliary contact-s are thereafter maintained in an open position while the main contacts are permitted to reclose since the latter are normally spring-loaded to a closed position and are opened only when the compressed air is delivered from a suitable source such as a storage tank to the contacts. To re-connect the load to the power source it is then necessary to close only the auxiliary contacts. An example of this type of application for the auxiliary contacts can be found in my prior United States Patent No. 2,708,700, granted May 17, 1955. In a modification of the foregoing arrangement, a current diminishing resistance may be connected permanently in parallel with the main contacts, in which case the auxiliary contacts have the additional function of interrupting the current flow through the resistance after the main contacts have been opened.

The auxiliary contacts are also used to connect and disconnect resistances in parallel with the main contacts, these resistances serving to control the voltage distribution across the main contacts when the latter comprise several sets of contacts arranged in series. An example of the latter application can be found in my prior United States Patent No. 2,453,555, granted November 9, 1948.

The switching of the main contacts is accomplished by means of the compressed gas and the switching of the auxiliary contacts can also be done by the compressed gas when the latter are used to connect and disconnect potential control resistances in parallel with the main contacts. When the auxiliary contacts function as an isolating switch, they can be actuated by mechanical means or by compressed air. Moreover, with switches of very high disconnecting capacity it is often necessary to blow compressed gas across the gap established between the auxiliary contacts as they separate in order to obtain a flawless arc extinction characteristic.

The use of auxiliary contacts and the compressed gas associated therewith normally increases the demand and use of the compressed gas, and attempts have been made to conserve the gas by utilizing the pressure drop in the gas which obtains when the latter is released from its supply source, usually a tank, to actuate the main contacts. For this purpose, it has been known to place the auxiliary contacts in an auxiliary chamber which is connected with the storage tank for the compressed gas, the chamber being charged with the compressed gas to the pressure within the tank. Then as the compressed gas 2,873,331 Patented Feb. 10, 1959 is released from the tank for flow to the main contacts, the resulting pressure drop within the tank establishes a pressure differential between it and the auxiliary chamber, which then causes the compressedgas stored in the auxiliary chamber to flow from the same past the auxiliary contacts into the storage tank. Such an arrangement, while conserving use of compressed gas, has a disadvantage in that the disconnecting capacity of the auxiliary contacts is dependent upon the consumption of the compressed gas at the main contacts of the switch. Such gas consumption or use is not uniform and hence the correspondingreduction in gas pressure within the storage tank is not uniform and hence the disconnecting capacity of the auxiliary contacts is also not uniform and thus interruption at the auxiliary contacts cannot always be assured. Moreover, since the compressed gas in the auxiliary chamber in which the auxilary contacts are located serves as an arc extinction chamber, there always exists the danger that gases generated by the arc will flow back into the compressed gas storage tank from which they can pass, at subsequent opening operations of the switch, to the main contacts themselves thus possibly interfering with proper interruption of the main load currents at these contacts.

The present invention relates to an arrangement wherein the compressed gas flow associated with the auxiliary contacts is also made dependent upon a pressure differential created when the compressed gas flows to the main contacts but wherein the gases formed by the arc established upon separation of the auxiliary contacts are rendered harmless. Moreover, an aspirating etiect is established to augment the pressure differential in order to draw the compressed gas from the auxiliary chamber past the gap established between the auxiliary contacts as the latter open.

In particular, the chamber containing the auxiliary contacts is located laterally of and in communication with the duct which conveys the compressed gas from the storage tank to the main contacts. This duct is also in communication with the storage tank when the main contacts are closed and hence is charged with compressed gas to the pressure prevailing within the tank in advance of opening the main contacts. When the main contacts are to be opened, the flow of the compressed gas through the duct from the storage tank to the main contacts establishes a pressure differential between the duct and the auxiliary chamber and the compressed gas stored therein is permitted to flow outwardly from the same into the duct. Moreover, upon leaving the auxiliary chamber, the gas is caused to pass through a cooling means which renders it harmless. In addition to the pressure differential efiect, the flow of the compressed gas past the auxiliary contacts and out of the auxiliary chamber is augmented by an aspirating effect caused by the flow of gas through the duct past the mouth of the passageway leading from the same to the auxiliary chamber.

.The foregoing objects and advantages will becom more apparent from the following description of one application of the inventive concept and the accompanying drawings, Fig. 1 being a view partly in elevation and partly in vertical section and Fig. 2 a section on line 2-2 of Fig. 1.

With reference now to the drawing, the switch assembly is seen to include an elongated compressed air tank 1 upon which the remainder of the switch components upstand. The hollow electrical insulator column 2 which extends upwardly from tank 1 and communicates with divided by a transverse wall 6 into a lower vertical conductive material end of this sleeve tacts is bathed on all sides -material is attached to and forms an electrically Conductive tubular member "drical end cap 33 of electrically conductive material is attached to and closes off the outer end 3, trically conductive material, and within the tubular sectron 4 is an inner cylindrical member 5 also made of electrically conductive material and which is likewise supported by the top wall of housing 3. Member 5 is cylinder 7 containing a vertically slidable piston 8 loaded to an upward position by a spring 9, and an upper vertical cylinder 1%) containing a vertically slidable piston 11 made of electrically conductive material and loaded to an upward position by a spring 12. The piston 11 serves as a movable pin contact and is normally engaged with and closes the mouth of a stationary nozzle contact member 13. The latter islikewise made of electrically and provided with an outer peripheral depending end flange 14 supported by the upper end of a cylindrical sleeve of insulating material, the lower being supported upon the upper end of the cylindrical member 4 and the interior of the sleeve 15 serving as an arc chamber for the main contacts 11 and 13. As indicated in the drawing, the upper end of the pin contact 11 is rounded to form a nose portion which engages and closes off the mouth of the nozzle contact 13. When compressed air is permitted to flow upwardly into the interior of sleeve 15, it forces the pin contact 11 downwardly against the restoring action of its loading spring 12 so as to separate it from the nozzle contact 13 and the ensuing are drawn between the conand extinguished by the flow of the compressed air across the nose of the pin contact 11 and upwardly through the interior of the nozzle contact 13.

Entry of the compressed air to the sleeve 15 is controlled by a normally closed valve 16 which is actuated by piston 8 in the lower cylinder 7. Valve 16 is shown as being of the poppet type, the valve head 17 being connected to the piston rod 18 and the valve operating with a seat 19 formed in the top wall of the housing 3. For actuating piston 8 in the downward direction to cause it to open valve 16, it will be seen that compressed air is lead' into the upper end of cylinder 7 from the tank 1 by a controlling valve 21, an upright hollow insulator column 22 which communicates with the discharge side of valve 21 and a pipe 23 connected to the upper end of the column 22, the upper end of pipe 23 terminating in communication with the interior of cylinder 7.

In the illustrated embodiment, a current reducing resistance element 24 is with the set of main contacts 11, 13, it being clear from the drawing that the resistance element 24 is supported in a vertical attitude laterally outward from the upright switch structure by electrically conductive brackets 25, 26 which engage the opposite ends of the resistance element 24, the lower bracket 25 being attached to the tubular section 4 which is connected electrically to the pin contact 11 via the top wall of housing 3 and the inner cylindrical member 5, and the upper bracket 26 being atconnected electrically in parallel head 17 cotached to the nozzle contact 13 structure directly. A

main terminal T1 of the switch is electrically connected to the upper bracket 26.

The auxiliary contacts of the switch are carried in an assembly which is attached to and extends laterally outward from one side wall of the housing'3. This assembly includes a horizontally extending cylindrical tubular member 27 of electrically conductive material having an end flange 28 which is attached to the marginal portion of a circular opening 29 in a side wall of the housing 3. Formed within the member 27 is a horizontally extending cylindrical tubular member 31 concentric with the outer tubular member 27. A sleeve 32 of insulating extension of the 27 and a cylinof the insulatin shown in full and broken --ment of lever 45. The

main contacts sleeve 32. The end cap 33 has attached to it the other terminal T2 of the switch and also supports within the same an axially extending stationary auxiliary contact member 34, the latter being located Within an arcing chamber 39 formed by the interior of the assembly comprising the tubular member 27, tubular insulating sleeve 32 and end cap 33.

A movable pin auxiliary contact member 35 cooperating with the stationary auxiliary contact member 34 is supported for horizontal sliding movement within the inner tubular member 31, it being noted from the drawing that the outer end of the latter is closed except for a central opening 36 through which the pin contact 35 is adapted to pass. In the position shown in full lines, the pin contact 35 projects through the central opening 36 and engages the stationary contact member 34. The inner end of the tubular member 31 includes an assembly of cooling plates 37 arranged next to each other and which have small spaces between them andtthe compressed air which passes outward through these plates from chamber 39 and thence into the housing 3 is cooled by contact with the-plates. A small port 38 in a wall portion of the tubular member 27 places the interior of the latter and hence the arcing chamber 39 for the contacts 34, 35 with the interior of housing 3 and it is through the port 38 that the arcing chamber 39 is filled with compressed air when the main contacts 11, 13 are closed, it being noted that under such circumstances, valve 16 is closed and housing 3 is filled with compressed air from the tank 1. Consequently, the pressure of the air in the arcing chamber 39 is then equal to that prevailing in the housing 3.

The movable contact member 35 is arranged to be moved longitudinally of itself between the positions lines respectively by linkage 41 consisting of interconnected levers and links. A link 42, connecting the lower actuating lever 43 with the upper coupled levers 44, 95, the lever t5 being pivotally connected to slidable contact member 35, is made out of insulating material in order to insulate the contacts from ground. The lever 45 which is articulated to contact pin 35 passes through a packed slot 46 in the lower wall portion of the cylindrical member 31 to enable moveelectrical connection from terminal T2 can be traced through the end cap 33, stationary contact member 34, movable contact member 35, the inner tubular member 31 with which the contact member 35 is slidably engaged, and the outer tubular member 27 which is attached to housing 3. From the latter, the circuit extends through the cylindrical member 5 and 11, 13 to terminal T1, and also through the tubular section 4 and resistance 24 to the terminal TI. This places the main contacts 11, 13 and the auxiliary contacts 34, 35 in series between terminals T1, T2.

Operation The switch assembly according to the invention operates in the following manner:

When it is desired to open the switch, valve 21 is opened thus admitting compressed air from the tank 1 upwardly through insulator column 22 and pipe 23 to the interior of the lower cylinder 7 causing piston 8 to be driven downwardly and thereby open. valve 16. Compressed air then fiows upwardly through insulator column 2 and housing 3 and through valve 16 and upwardly through the annular space between the cylindrical member 5 and the tubular section 4 and insulator 15. The air pressure then obtaining at the junction of the pin contact 11 with the nozzle contact 13 causes the pin contact 11 to move downwardly to the position indicated by broken lines and separate from the nozzle -contact 13 thus interrupting the main path of flow of through the resistance'element 24.

After the main contacts 11, 13 have been separated, the linkage 41 is actuated thus moving the contact pin 35 to the left and to the position indicated by broken lines thus separating it from the stationary contact member 34. The compressed air which has been stored within the arcing chamber 39 at the pressure prevailing in the tank 1 before the control valve 16 was opened will now be at a higher pressure than the air flowing upwardly through housing 3 to the main contacts and hence the compressed air stored within chamber 39 will now flow past the separated auxiliary contacts 34, 35 assisting in the extinction of the are drawn therebetween upon separation and through the opening 36 and through the interior of the cylindrical member 31 and past the cooling plates 37 into the housing 3 thus cooling and purifying the air which enters housing 3 from the arcing chamber 39. In addition to the pressure differential effect which induces the flow of compressed air outwardly from arcing chamber 39, the flow of compressed air upwardly through housing 3 from tank 1 past the wall opening 29 creates an aspirating effect which tends to also suck the compressed air outwardly from arcing chamber 39. The main control valve 21 is now reclosed thus closing valve 16 as piston 8 moves upward by the force of its biasing spring 9 and stopping the flow of compressed air upwardly from housing 3. This permits the main pin contact 11 to move upward by the force of its biasing spring 12 and reengage the nozzle contact 13. The auxiliary contacts 34, 35 remain open. The switch is thus in its disconnected state. Compressed air from tank 1 and housing 3 then flows 'back into the arcing chamber 39 through the port 38 and aperture 36 until the air pressure in chamber 39 is once again equal to that prevailing in-housing 3. When the switch is closed by closing the auxiliary contacts 34, 35, the

aperture 36 will be cut oif. However, the compressed air in chamber 39 will remain at the same pressure as the air in housing 3 with valve 16 closed because of the permanently open port 38. If the gas pressure in tank 1 changes while valve 16 is closed, the gas pressure in chamber 39 will then undergo a corresponding change.

The supply line for the main, power interrupting contacts is carried out in rectangular form, the main contacts being thereby built up in the direction of the inlet while the auxiliary contacts lie at right angles to this. If the switching apparatus includes several sets of auxiliary contacts, for example for switching resistances or for the switching of several branches, then the supply line is carried out in elongated rectangular form and the main contacts thereby attached on the narrow side of the rectangle, the sets of auxiliary contacts being located along the long side of this rectangle.

It is also possible to provide an arrangement wherein the compressed air supply tank is not insulated from the voltage prevailing at the main and auxiliary contacts. With such a constrution the contacts can then be mounted directly upon the compressed air tank and the latter is then properly insulated from ground.

Also, in conclusion it is desired to point out that while the invention has been illustrated in its application to a compressed air operated switching assembly wherein the auxiliary contacts are arranged in series with the main contacts, the same inventive concept can be applied to other types of compressed air operated switching apparatus which include auxiliary contacts having compressed air supplied thereto to facilitate arc extinction, such as for example the type referred to at the beginning of the specification wherein the auxiliary contacts are used for switching resistances associated with the main contacts for potential control.

I claim:

1. A compressed gas actuated electric switch comprising a supply tank containing gas under pressure, a switch contact assembly comprising normally closed main contact means and which are separated upon application thereto of compressed gas, means forming a primary passageway interconnecting said supply tank and main contact means, normally closed valve means controlling flow of compressed gas through said passageway, auxiliary contact means arranged within an arcing chamber, means for charging said chamber with compressed gas from said tank to the pressure prevailing in said tank when said valve is closed, means forming a secondary passageway leading from said chamber to and intersecting said primary passageway at an angle thereby to establish an aspirating effect on the compressed gas in said chamber, said secondary passageway being normally closed but which is open upon separation of said auxiliary contact means subsequent to opening of said valve to initiate gas flow through said primary passageway, said compressed gas blowing on said auxiliary contact means as it leaves said chamber and flows through said secondary passageway.

2. A compressed gas actuated electric switch as defined in claim 1 and which further includes means in said secondary passageway for cooling the compressed gas withdrawn from said chamber by said aspirating effect.

3. A compressed gas actuated electric switch as defined in claim 2 wherein said gas cooling means is constituted by a plurality of metallic cooling plates having openings through which said gas is passed prior to reaching said primary passageway.

4. A compressed gas actuated electric switch as defined in claim 1 wherein said secondary passageway is disposed normal to said primary passageway and one of said auxiliary contact means is constituted by a contact pin arranged within said secondary passageway and slidably mounted to project through an aperture in an end wall of said secondary passageway for engagement with another auxiliary contact in said chamber, and means for actuating said contact pin to withdraw the same from said aperture thus initiating outward flow therethrough of compressed gas from said chamber.

5. A compressed gas actuated electric switch as defined in claim 1 wherein said means for charging said chamber with compressed gas from said tank is constituted by a port interconnecting said chamber with said primary passageway at a point intermediate said control valve means and said tank.

6. A compressed gas actuated electric switch as defined in claim 1 wherein said primary passageway is incorporated in a structure of elongated rectangular form,

References Cited in the file of this patent UNITED STATES PATENTS 2,627,005 Baker et al Ian. 27, 1953 2,678,983 Strom May 18, 1954 2,763,754 Latour Sept. 18, 1956 

